JP2017072420A - Structure monitoring system and structure monitoring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure monitoring system and a structure monitoring method capable of accurately monitoring soundness (state) of a structure including metal part.SOLUTION: Disclosed structure monitoring system 1 includes: a magnetic sensor 2 that detects the strength of magnetic field from a structure which includes a metal part by using characteristics of energy transition of an alkaline metal atom; and a control unit 53 that determines the soundness (degree of fatigue of the metal part) of the structure by using the detection result by the magnetic sensor 2.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a structure monitoring system and a structure monitoring method.

  A structure monitoring system that monitors the soundness of a structure including a metal part such as a reinforcing bar or steel frame is known (see, for example, Non-Patent Document 1).

  For example, in the system described in Non-Patent Document 1, an acceleration sensor is installed in a structure, and the state (soundness) of the structure is confirmed using the detection result of the acceleration sensor.

Koichi Sato and three others, "Basic study for development of structural monitoring system", Taisei Construction Technology Center Bulletin, Taisei Corporation, 2010, No. 43

  Although the system described in Non-Patent Document 1 can capture a vibration abnormality of a structure that has occurred as a result of deterioration of a reinforcing bar included in the structure, the cause of the vibration abnormality (for example, vibration due to deterioration of the reinforcing bar) There was a problem that it was not possible to specify whether or not it was abnormal.

  The objective of this invention is providing the structure monitoring system and structure monitoring method which can monitor the soundness (state) of the structure containing a metal part more correctly.

Such an object is achieved by the present invention described below.
The structure monitoring system of the present invention includes a magnetic sensor that detects a magnetic field from a structure including a metal part using the energy transition characteristics of alkali metal atoms,
And a determination unit that determines the soundness of the structure using a detection result of the magnetic sensor.

  According to such a structure monitoring system, the magnetic field from the structure including the metal part (more specifically, the magnetic field generated from the metal part due to metal fatigue) using the energy transition characteristics of alkali metal atoms. The fatigue state of the metal part of the structure can be determined using a magnetic sensor that detects the above. Therefore, information on the fatigue state of the metal part can be included in the determination result of the soundness of the structure, and as a result, the soundness (state) of the structure including the metal part can be monitored more accurately.

The structure monitoring system of the present invention includes a vibration sensor for detecting vibration of the structure,
Preferably, the determination unit determines the soundness level using a detection result of the vibration sensor in addition to a detection result of the magnetic sensor.

  Thereby, the information regarding the presence or absence of vibration abnormality of the whole structure can be included in the determination result of the soundness level of the structure.

The structure monitoring system of the present invention includes a storage unit that stores vibration data related to the natural vibration of the structure,
The determination unit preferably compares the detection result of the vibration sensor with the vibration data, and determines the soundness level using the comparison result.

  Thereby, the presence or absence of vibration abnormality of the whole structure can be determined easily and accurately and included in the determination result of the soundness level of the structure.

  In the structure monitoring system according to the aspect of the invention, it is preferable that the determination unit determines a fatigue level of the metal part using a detection result of the magnetic sensor.

  Thereby, the information regarding the fatigue state of a metal part can be included in the determination result of the soundness level of the structure.

In the structure monitoring system of the present invention, the magnetic sensor includes:
An atomic cell encapsulating an alkali metal;
A light source unit for irradiating light to the atomic cell;
A light detection unit for detecting the light transmitted through the atomic cell,
A unit body including the atomic cell, the light source unit, and the light receiving unit is preferably attached to the structure.

  Thereby, a magnetic sensor using a nonlinear magneto-optical effect or an electromagnetically induced transmission phenomenon can be realized. Also, the atomic cell can be installed near the metal part, and as a result, the magnetic field from the metal part can be detected with high accuracy.

In the structure monitoring system of the present invention, the magnetic sensor includes a circuit unit electrically connected to the light source unit and the light detection unit,
It is preferable that the circuit part is separated from the main body part.

  Thereby, the unit including the atomic cell can be set inside the structure with respect to the circuit unit, and the unit can be easily installed near the metal unit.

  In the structure monitoring system of the present invention, it is preferable that the atomic cell is included in the metal part when viewed from the direction in which the atomic cell and the metal part are arranged.

  Thereby, the magnetic field from a metal part can be made to act on an atomic cell suitably. Therefore, the magnetic field from a metal part can be detected with high accuracy using a magnetic sensor.

  In the structure monitoring system of the present invention, it is preferable to include a communication unit that wirelessly transmits the detection result of the magnetic sensor.

  Thereby, even when there are a plurality of magnetic sensors, the detection results of the magnetic sensors can be easily collected.

  In the structure monitoring system of the present invention, it is preferable that the communication unit is driven by power from a battery.

  Thereby, even in an environment without a commercial power source, the magnetic field from the structure can be detected using the magnetic sensor, and the soundness level of the structure can be monitored using the detection result.

  In the structure monitoring system of the present invention, it is preferable that the magnetic sensor detects the intensity of a magnetic field using a nonlinear magneto-optical effect of the alkali metal atom.

  Thereby, the magnetic field from a metal part can be detected with high precision using a magnetic sensor.

  In the structure monitoring system of the present invention, it is preferable that the magnetic sensor detects a magnetic field intensity using an electromagnetically induced transmission phenomenon of the alkali metal atom.

  Thereby, the magnetic field from a metal part can be detected with high precision using a magnetic sensor.

The structure monitoring method of the present invention includes a step of preparing a magnetic sensor for detecting the strength of a magnetic field using the energy transition characteristics of alkali metal atoms,
Attaching the magnetic sensor to a structure including a metal part;
Detecting a change in the magnetic field due to fatigue of the metal part using the magnetic sensor;
And determining the soundness of the structure using the detection result of the magnetic sensor.

  According to such a structure monitoring method, a magnetic field from a structure including a metal part (more specifically, a magnetic field generated by metal fatigue from a metal part) using the energy transition characteristics of alkali metal atoms. The fatigue state of the metal part of the structure can be determined using a magnetic sensor that detects the above. Therefore, information on the fatigue state of the metal part can be included in the determination result of the soundness of the structure, and as a result, the soundness (state) of the structure including the metal part can be monitored more accurately.

It is a figure which shows an example of the use condition of the structure monitoring system which concerns on 1st Embodiment of this invention. It is a block diagram which shows schematic structure of the structure monitoring system shown in FIG. It is a figure which shows the installation state of the magnetic sensor with which the structure monitoring system shown in FIG. 1 is provided. It is sectional drawing of the sensor main-body part with which the magnetic sensor shown in FIG. 3 is provided. It is a block diagram which shows the control system of the magnetic sensor shown in FIG. It is a graph which shows the relationship between the magnetic flux density of a cesium atom, and an energy transition state. It is a graph which shows the relationship between the distortion of the metal part contained in a structure, and the intensity | strength of the magnetic field produced in connection with it. It is a graph which shows the relationship between the magnetic field detected by a magnetic sensor, and the amount of vibrations detected by a vibration sensor. It is a flowchart for demonstrating the usage method (structure monitoring method) of the structure monitoring system shown in FIG. It is a figure which shows schematic structure of the magnetic sensor used for the structure monitoring system which concerns on 2nd Embodiment of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a structure monitoring system and a structure monitoring method of the present invention will be described with reference to the accompanying drawings.

<First Embodiment>
First, a first embodiment of the present invention will be described.

≪Structure monitoring system≫
FIG. 1 is a diagram illustrating an example of a usage state of the structure monitoring system according to the first embodiment of the present invention. FIG. 2 is a block diagram showing a schematic configuration of the structure monitoring system shown in FIG. FIG. 3 is a diagram illustrating an installation state of the magnetic sensor included in the structure monitoring system illustrated in FIG. 1. FIG. 4 is a cross-sectional view of a sensor main body included in the magnetic sensor shown in FIG. FIG. 5 is a block diagram showing a control system of the magnetic sensor shown in FIG. FIG. 6 is a graph showing the relationship between the magnetic flux density of cesium atoms and the energy transition state.

  A structure monitoring system 1 shown in FIG. 1 (hereinafter simply referred to as “system 1”) monitors the soundness (state) of the structure B. The system 1 includes a sensor device 4 that measures the state of the structure B, and a collection device 5 (logger) that collects the measurement results of the sensor device 4.

  Here, the structure B is a building structure of a three-story reinforced concrete structure or a reinforced steel concrete structure for convenience of explanation. The sensor device 4 includes a plurality of magnetic sensors 2 (2a, 2b, 2c) installed on the walls W (W1, W2, W3) of each floor of the structure B, and a floor F (F1) of each floor of the structure B. , F2, F3) and a plurality of vibration sensors 3 (3a, 3b, 3c). In the sensor device 4, each magnetic sensor 2 detects the magnetic field from the metal part of the structure B, and each vibration sensor 3 detects the vibration of the structure B, and transmits these detection results to the collection device 5. To do.

  The collection device 5 collects the detection results transmitted from the sensor device 4 and determines the soundness of the structure B using the collected detection results. The determination result is displayed, for example, on a display device (not shown), or taken in a personal computer, a portable terminal, or the like.

Hereinafter, the sensor device 4 and the collection device 5 will be sequentially described in detail.
(Sensor device)
As shown in FIG. 2, the sensor device 4 includes a plurality of magnetic sensors 2, a plurality of vibration sensors 3, a communication unit 41 that transmits detection results of these sensors, a storage unit 42, a control unit 43, Have

[Magnetic sensor]
The magnetic sensor 2 has a function of detecting the strength of the magnetic field from the structure B using the energy transition characteristics of alkali metal atoms. The magnetic sensor 2 is installed on the wall W as shown in FIG. Here, the wall W is composed of a metal part ST such as a reinforcing bar and a concrete part C that reinforces the metal part ST, and at least a part of the magnetic sensor 2 (main body part 20) is a concrete part C of the wall W. It is buried in.

  As shown in FIG. 4, the main body portion 20 of the magnetic sensor 2 is housed in the atomic cell unit 22 that generates the quantum interference effect as described above, the package 21 that houses the atomic cell unit 22, and the package 21. And a support member 23 that supports the atomic cell unit 22 with respect to the package 21. Although not shown, a coil (coil 231 shown in FIG. 5) is disposed inside or outside the package 21 so as to surround the atomic cell unit 22.

  The atomic cell unit 22 includes an atomic cell 221, a light source unit 222, optical components 223 and 224, a light detection unit 225, a heater 226, a temperature sensor 227, a substrate 228, and a holding member 229. These are unitized. Specifically, the light source unit 222, the heater 226, the temperature sensor 227, and the holding member 229 are mounted on the upper surface of the substrate 228, and the atomic cell 221 and the optical components 223 and 224 are held by the holding member 229. The light detection unit 225 is joined to the holding member 229 via the adhesive 230.

Hereinafter, each part of the main body 20 of the magnetic sensor 2 will be described.
The atomic cell 221 is filled with gaseous alkali metal such as rubidium, cesium, and sodium. Further, in the atomic cell 221, a rare gas such as argon or neon, or an inert gas such as nitrogen may be sealed together with an alkali metal gas as a buffer gas, if necessary.

  As shown in FIG. 4, the atomic cell 221 includes a body portion 2211 having a columnar through hole, and a pair of light transmitting portions 2212 and 2213 that block openings on both sides of the through hole. Thereby, the internal space S in which the alkali metal as described above is enclosed is formed.

  Here, each of the light transmission parts 2212 and 2213 of the atomic cell 221 has transparency to the light (resonant light pair) from the light source part 222. The material constituting the light transmitting portions 2212 and 2213 is not particularly limited as long as it has transparency to the excitation light as described above, and examples thereof include glass materials and quartz.

  Further, the material forming the body portion 2211 of the atomic cell 221 is not particularly limited, and may be a silicon material, a ceramic material, a metal material, a resin material, or the like, and a glass material, like the light transmitting portions 2212 and 2213, It may be a crystal or the like.

  The light transmission parts 2212 and 2213 are airtightly joined to the body part 2211. Thereby, the internal space S of the atomic cell 221 can be made an airtight space. The bonding method of the body portion 2211 and the light transmission portions 2212 and 2213 of the atomic cell 221 is determined according to these constituent materials and is not particularly limited. For example, a bonding method using an adhesive or a direct bonding method is used. An anodic bonding method or the like can be used.

  The light source unit 222 emits resonance light pairs (resonance light 1 and resonance light 2) that are two types of light having different frequencies that resonate with the alkali metal atoms in the atomic cell 221 described above. The light source unit 222 is not particularly limited as long as it can emit light as described above. For example, a semiconductor laser such as a vertical cavity surface emitting laser (VCSEL) can be used.

An alkali metal has a three-level system energy level and can take three states of two ground states (ground states 1 and 2) having different energy levels and an excited state. Here, the ground state 1 is a lower energy state than the ground state 2. When the two kinds of resonance lights 1 and 2 emitted from the light source unit 222 are irradiated onto the alkali metal, the difference is determined according to the difference (ω ₁ −ω ₂ ) between the frequency ω ₁ of the resonance light ₁ and the frequency ω ₂ of the resonance light 2. Thus, the light absorptivity (light transmittance) of the resonance light 1 and 2 in the alkali metal changes.

When the difference (ω ₁ −ω ₂ ) between the frequency ω ₁ of the resonant light ₁ and the frequency ω ₂ of the resonant light 2 coincides with the frequency corresponding to the energy difference between the ground state 1 and the ground state 2, the ground state Excitation from 1, 2 to the excited state stops. At this time, both the resonant lights 1 and 2 are transmitted without being absorbed by the alkali metal. Such a phenomenon is called a CPT phenomenon or an electromagnetically induced transparency (EIT) phenomenon.

For example, when the frequency ω ₁ of the resonant light ₁ is fixed and the frequency ω ₂ of the resonant light 2 is changed, the difference between the frequency ω ₁ of the resonant light ₁ and the frequency ω ₂ of the resonant light 2 (ω ₁ −ω _{When 2} ) coincides with the frequency ω ₀ corresponding to the energy difference between the ground state 1 and the ground state 2, the detection intensity of the light detection unit 225 increases sharply with the EIT phenomenon described above. Such a steep signal is detected as an EIT signal. This EIT signal has an eigenvalue determined by the type of alkali metal.

  As shown in FIG. 4, the plurality of optical components 223 and 224 are respectively provided on the optical path of light between the light source unit 222 and the atomic cell 221 described above. In the present embodiment, the optical component 223 and the optical component 224 are arranged in this order from the light source unit 222 side to the atomic cell 221 side.

  The optical component 223 is a λ / 4 wavelength plate. Thereby, the light (excitation light) from the light source unit 222 can be converted from linearly polarized light into circularly polarized light (right circularly polarized light or left circularly polarized light). In a state where the alkali metal atoms in the atomic cell 221 are Zeeman split by the magnetic field of the coil 231 shown in FIG. 5, when the alkali metal atoms are irradiated with circularly polarized excitation light, the interaction between the excitation light and the alkali metal atoms causes alkali Of the plurality of levels in which the metal atom is Zeeman split, the number of alkali metal atoms at a desired energy level can be made relatively larger than the number of alkali metal atoms at other energy levels. Therefore, the number of atoms that express the desired EIT phenomenon increases, and the intensity of the desired EIT signal increases.

  The coil 231 may be a solenoid coil or a Helmholtz coil. The magnetic field generated by the coil 231 has a constant magnitude (or amplitude), and may be either a DC magnetic field or an AC magnetic field, or a magnetic field obtained by superimposing a DC magnetic field and an AC magnetic field. There may be.

  The optical component 224 is a neutral density filter (ND filter). Thereby, the intensity of light incident on the atomic cell 221 can be adjusted (decreased).

  In addition to the wave plate and the neutral density filter, other optical components such as a lens and a polarizing plate may be disposed between the light source unit 222 and the atomic cell 221. Further, the optical component 224 can be omitted depending on the intensity of light from the light source unit 222.

  The light detection unit 225 has a function of detecting the intensity of excitation light (resonance light 1 and 2) transmitted through the atomic cell 221. The light detector 225 is not particularly limited as long as it can detect the excitation light as described above. For example, a photodetector (light receiving element) such as a solar cell or a photodiode can be used.

  The heater 226 includes a heating resistor (heating unit) that generates heat when energized. Heat from the heater 226 is transmitted to the atomic cell 221 through the substrate 228 and the holding member 229.

  The temperature sensor 227 detects the temperature of the heater 226 or the atomic cell 221. Based on the detection result of the temperature sensor 227, the amount of heat generated by the heater 226 is controlled. Thereby, the alkali metal atom in the atomic cell 221 can be maintained at a desired temperature.

  In the present embodiment, the temperature sensor 227 is provided on the substrate 228. The installation position of the temperature sensor 227 is not limited to this. For example, the temperature sensor 227 may be on the holding member 229, on the heater 226, or on the outer surface of the atomic cell 221. Good.

  The temperature sensor 227 is not particularly limited, and various known temperature sensors such as a thermistor and a thermocouple can be used.

  The holding member 229 thermally connects the heater 226 and the light transmission parts 2212 and 2213 of the atomic cell 221. Thereby, the heat from the heater 226 can be transmitted to the light transmission parts 2212 and 2213 by heat conduction by the holding member 229, and the light transmission parts 2212 and 2213 can be heated.

  As a constituent material of such a holding member 229, it is preferable to use a material excellent in thermal conductivity, for example, a metal material. Further, similarly to the package 21 to be described later, it is preferable to use a non-magnetic material as a constituent material of the holding member 229 so that the magnetic field from the outside to the atomic cell 221 and the magnetic field from the coil 231 are not inhibited.

  The substrate 228 has a function of supporting the light source unit 222, the heater 226, the temperature sensor 227, the holding member 229, and the like described above. The substrate 228 has a function of transmitting heat from the heater 226 to the holding member 229. Thereby, even if the heater 226 is separated from the holding member 229, the heat from the heater 226 can be transmitted to the holding member 229.

  Here, the substrate 228 thermally connects the heater 226 and the holding member 229. By mounting the heater 226 and the holding member 229 on the substrate 228 in this manner, the degree of freedom of installation of the heater 226 can be increased.

  Further, since the light source unit 222 is mounted on the substrate 228, the temperature of the light source unit 222 on the substrate 228 can be adjusted by heat from the heater 226.

  The substrate 228 includes wiring (not shown) that is electrically connected to the light source unit 222, the heater 226, and the temperature sensor 227.

  The constituent material of the substrate 228 is not particularly limited, and examples thereof include a ceramic material and a metal material. One of these materials can be used alone, or two or more materials can be used in combination. Note that an insulating layer made of, for example, a resin material, a metal oxide, a metal nitride, or the like is provided on the surface of the substrate 228 as necessary for the purpose of preventing a short circuit of a wiring included in the substrate 228, for example. May be. Further, similarly to the package 21 described later, it is preferable to use a non-magnetic material as the constituent material of the substrate 228 so as not to disturb the magnetic field from the outside to the atomic cell 221 and the magnetic field from the coil 231.

  The substrate 228 can be omitted depending on the shape of the holding member 229, the installation position of the heater 226, and the like. In this case, the heater 226 may be installed at a position in contact with the holding member 229.

  As shown in FIG. 4, the package 21 has a function of accommodating the atomic cell unit 22 and the support member 23. The package 21 may contain components other than the components described above.

  As shown in FIG. 4, the package 21 includes a plate-shaped base 211 (base portion) and a bottomed cylindrical lid 212 (lid), and the opening of the lid 212 is sealed by the base 211. Has been. Thereby, an internal space S <b> 1 for accommodating the atomic cell unit 22 and the support member 23 is formed.

  The base 211 supports the atomic cell unit 22 via the support member 23. The base 211 is a wiring board, for example, and a plurality of terminals 214 are provided on the lower surface of the base 211. Although not shown, the plurality of terminals 214 are electrically connected to a plurality of terminals provided on the upper surface of the base body 211 through wiring penetrating the base body 211. The light source unit 222 and the substrate 228 described above are electrically connected to the base 211 via wiring (not shown) (for example, a flexible wiring substrate or a bonding wire).

  The constituent material of the substrate 211 is not particularly limited. For example, a resin material, a ceramic material, or the like can be used, but a ceramic material is preferably used. Thereby, the airtightness of the internal space S1 can be improved while realizing the base body 211 constituting the wiring board.

  A lid 212 is joined to such a base 211. A method for joining the base body 211 and the lid body 212 is not particularly limited. For example, brazing, seam welding, energy beam welding (laser welding, electron beam welding, etc.), or the like can be used. A joining member for joining these may be interposed between the base body 211 and the lid body 212.

  Moreover, it is preferable that the base body 211 and the lid body 212 are airtightly joined. That is, the inside of the package 21 is preferably an airtight space. Thereby, the inside of the package 21 can be made into a pressure-reduced state, As a result, the characteristic of the main-body part 20 can be improved. In particular, the inside of the package 21 is preferably in a reduced pressure state (vacuum). Thereby, the characteristic of the main-body part 20 can be improved more.

  The constituent material of the lid 212 is not particularly limited as long as it has magnetic permeability and can form an airtight space as described above. For example, a resin material, a ceramic material, a metal material, or the like can be used. Can be used.

  The support member 23 (support portion) is housed in the package 21 and has a function of supporting the atomic cell unit 22 with respect to the package 21 (more specifically, the base body 211 constituting a part of the package 21). Have The support member 23 has a function of suppressing heat transfer between the atomic cell unit 22 and the outside of the package 21. Thereby, the thermal interference between each part of atomic cell unit 22 and the exterior can be controlled.

  Such a support member 23 is bonded to each of the base body 211 and the substrate 228 of the package 21 by, for example, an adhesive.

The constituent material of the support member 23 is not particularly limited. For example, it is preferable to use a nonmetal such as a resin material or a ceramic material, and it is more preferable to use a resin material. Further, as the constituent material of the support member 23, it is preferable to use a non-magnetic material so as not to disturb the magnetic field from the outside to the atomic cell 221 and the magnetic field from the coil 231.
The configuration of the main body 20 of the magnetic sensor 2 has been described above.

  As shown in FIG. 5, in addition to the main body 20 described above, the magnetic sensor 2 includes a central wavelength control unit 244, an amplifier 240, a detection unit 241, a modulation unit 242, an oscillator 243, a detection unit 250, an oscillator 251, and a modulation unit. 252, an oscillator 253, a frequency converter 254, a detector 255, an oscillator 256, a modulator 257, an oscillator 258, and a modulator 259. These constitute a “circuit unit” electrically connected to the light source unit 222 and the light detection unit 225.

  The laser light emitted from the light source unit 222 is controlled based on the output of the center wavelength control unit 244 and the center wavelength λ 0 and is modulated based on the output of the modulation unit 259. For example, when a laser driver that supplies a drive current to the light source unit 222 is used as the center wavelength control unit 244, a laser emitted from the light source unit 222 by superimposing an alternating current output from the modulation unit 259 on the drive current. Modulate light. Then, as will be described later, the output of the modulation unit 259 is feedback-controlled so that the light corresponding to the modulation component becomes the resonance light 1 or the resonance light 2 for the alkali metal atom.

  The output signal of the light detection unit 225 is amplified by the amplifier 240 and input to the detection unit 241, the detection unit 250, and the detection unit 255.

  The detector 241 synchronously detects the output signal of the amplifier 240 using the oscillation signal of the oscillator 243. The modulation unit 242 modulates the output signal of the detection unit 241 with the oscillation signal of the oscillator 243. The oscillator 243 may oscillate at a low frequency of about several tens Hz to several hundreds Hz, for example. Then, the center wavelength control unit 244 controls the center wavelength λ0 of the laser light emitted from the light source unit 222 in accordance with the output signal of the modulation unit 242. The center wavelength λ0 is stabilized by a feedback loop passing through the light source unit 222, the atomic cell 221, the light detection unit 225, the amplifier 240, the detection unit 241, the modulation unit 242, and the center wavelength control unit 244.

  The detector 250 synchronously detects the output signal of the amplifier 240 using the oscillation signal of the oscillator 253. The oscillator 251 is an oscillator whose oscillation frequency changes according to the magnitude of the output signal of the detection unit 250, and can be realized by, for example, a voltage controlled crystal oscillator (VCXO). The modulation unit 252 modulates the output signal of the oscillator 251 with the oscillation signal of the oscillator 253. The oscillator 253 may oscillate at a low frequency of about several tens Hz to several hundreds Hz, for example.

  The frequency conversion unit 254 outputs the output signal of the modulation unit 252 to 1/2 of the frequency difference corresponding to the energy difference between the two ground levels of the alkali metal atom with the magnetic quantum number m = 0 enclosed in the atom cell 221 ( In the case of a cesium atom, the signal is converted to a signal having a frequency equal to (9.1926 GHz / 2 = 4.5963 GHz). The frequency conversion unit 254 can be realized by, for example, a PLL (Phase Locked Loop) circuit. Note that the frequency conversion unit 254 outputs the output signal of the modulation unit 252 to a frequency difference (cesium atom) corresponding to an energy difference between two ground levels of an alkali metal atom having a magnetic quantum number m = 0 enclosed in the atom cell 221. In this case, the signal may be converted to a signal having a frequency equal to 9.1926 GHz.

  The detector 255 synchronously detects the output signal of the amplifier 240 using the oscillation signal of the oscillator 258. The oscillator 256 is an oscillator whose oscillation frequency changes according to the magnitude of the output signal of the detection unit 255, and can be realized by, for example, a voltage controlled crystal oscillator (VCXO). Here, the oscillator 256 oscillates at a frequency Δω (for example, about 1 MHz to 10 MHz) sufficiently small with respect to a frequency corresponding to the width of the Doppler spread of the excitation level of the alkali metal atom enclosed in the atomic cell 221. Modulator 257 modulates the output signal of oscillator 256 with the oscillation signal of oscillator 258. The oscillator 258 may oscillate at a low frequency of about several tens Hz to several hundreds Hz, for example.

  Modulator 259 modulates the output signal of frequency converter 254 with the output signal of modulator 257 (the output signal of modulator 257 may be modulated with the output signal of frequency converter 254). The modulation unit 259 can be realized by a frequency mixer (mixer), a frequency modulation (FM) circuit, an amplitude modulation (AM) circuit, or the like. As described above, the laser light emitted from the light source unit 222 is modulated based on the output of the modulation unit 259, and a plurality of resonance light 1 and resonance light 2 are generated.

  In the magnetic sensor 2 having such a configuration, when a magnetic field is applied to the atomic cell 221, as shown in FIG. 6, the ground level 1 (F = 3) and the ground level 2 (F = 4) of the alkali metal atom. However, it is divided into a plurality of Zeeman splitting levels having different magnetic quantum numbers m. In both the ground level 1 and the ground level 2, the energy difference Eδ between two Zeeman split levels whose magnetic quantum numbers m are different from each other by 1 is proportional to the strength of the magnetic field. Further, feedback control is applied so that the signal intensity of the output signal of the light detection unit 225 (the output signal of the amplifier 240) is maximized. The signal intensity of the output signal of the light detection unit 225 (the output signal of the amplifier 240) is maximized with respect to the frequency δ corresponding to the oscillation frequency Δω of the oscillator 256 and the energy difference Eδ of the Zeeman split level. This is when the relationship of 2 × δ × n = Δω or Δω × n = 2 × δ (n is a positive integer) (Δω = 2δ is desirable) is satisfied. That is, since the oscillation frequency Δω of the oscillator 256 is proportional to the intensity of the magnetic field, the intensity of the magnetic field can be detected by using the oscillation signal of the oscillator 256 as an output signal. Here, although the magnetic field is always generated by the coil 231, the intensity of the external magnetism is calculated by obtaining the relative frequency of the output signal on the basis of the oscillation frequency of the oscillator 256 when the intensity of the external magnetism is zero. be able to.

  As described above, the magnetic sensor 2 detects the strength of the magnetic field using the electromagnetically induced transmission phenomenon of alkali metal atoms. Thereby, the magnetic field from the metal part ST can be detected with high accuracy using the magnetic sensor 2.

  In addition, since the main body unit 20 which is a unit including the atomic cell 221, the light source unit 222, and the light detection unit 225 is attached to the structure B, the atomic cell 221 can be installed near the metal unit ST. The magnetic field from the metal part ST can be detected with high accuracy.

  Here, when viewed from the direction in which the atomic cell 221 and the metal part ST are arranged, the atomic cell 221 is preferably included in the metal part ST. Thereby, the magnetic field from metal part ST can be made to act on the atom cell 221 suitably. Therefore, the magnetic sensor 2 can be used to detect the magnetic field from the metal part ST with high accuracy.

  Further, it is preferable that the circuit unit electrically connected to the light source unit 222 and the light detection unit 225 is separated from the main body unit 20. Thereby, the main body part 20 including the atomic cell 221 can be set to the inside of the structure B with respect to the circuit part, and the main body part 20 can be easily installed near the metal part ST.

[Vibration sensor]
The vibration sensor 3 has a function of detecting the vibration of the structure B. The vibration sensor 3 is not particularly limited as long as it can detect vibrations. For example, the vibration sensor 3 includes an acceleration sensor, an angular velocity sensor, and the like.

[Communication Department]
The communication unit 41 illustrated in FIG. 2 has a function of wirelessly transmitting measurement information (hereinafter, also simply referred to as “measurement information”) including detection results of the magnetic sensor 2 and the vibration sensor 3 described above. The wirelessly transmitted measurement information is received by the collection device 5. The communication unit 41 may transmit information obtained by processing the detection results of the magnetic sensor 2 and the vibration sensor 3 by the control unit 43 as measurement information.

  Although not shown, the communication unit 41 includes an antenna and a communication circuit. Although an antenna is not specifically limited, For example, it is comprised with a metal material, carbon, etc., and makes | forms forms, such as a coil | winding and a thin film. The communication circuit includes, for example, a transmission circuit for transmitting electromagnetic waves and a modulation circuit having a function of modulating a signal to be transmitted. In addition, the communication circuit may include a down converter circuit having a function of converting a signal frequency to a low level, an up converter circuit having a function of converting a signal frequency to a large level, an amplifier circuit having a function of amplifying a signal, and the like. Good.

[Storage unit]
The storage unit 42 has a function of storing information such as the detection result of the magnetic sensor 2 and the detection result of the vibration sensor 3. This stored information is wirelessly transmitted by the communication unit 41 described above. Thereby, the communication part 41 can carry out the radio transmission of the detection result of the magnetic sensor 2 and the vibration sensor 3 over predetermined time collectively.

  Such a storage unit 42 is not particularly limited, and either a non-volatile memory or a volatile memory can be used. However, a state in which information is stored can be maintained without supplying power, thereby saving power. It is preferable to use a non-volatile memory from the viewpoint that the memory can be realized, and it is particularly preferable to use a flash memory from the viewpoint that information can be read and written with power saving.

[Control unit]
The control unit 43 has a function of controlling each unit constituting the sensor device 4 and processing information on detection results of the magnetic sensor 2 and the vibration sensor 3 as necessary. The control unit 43 is configured by an MPU, for example. In addition, this control part 43 may determine the soundness level of the structure B using the detection result of the magnetic sensor 2 and the vibration sensor 3 similarly to the control part 53 of the collection apparatus 5 mentioned later. In this case, information regarding the determination result may be transmitted by the communication unit 41.

  The configuration of the sensor device 4 has been described above. Although it does not specifically limit as a power supply which drives the sensor apparatus 4 comprised in this way, For example, the secondary battery etc. which were connected to the commercial power supply and the solar cell can be used.

  According to the sensor device 4 as described above, the communication unit 41 wirelessly transmits the detection results of the plurality of magnetic sensors 2, so that the detection results of the magnetic sensors 2 can be collected even when there are a plurality of magnetic sensors 2. 5 can be easily collected.

  Further, when the communication unit 41 is driven by power from the battery, the magnetic sensor 2 is used to detect the magnetic field from the structure B even in an environment without a commercial power source, and the detection result is used to detect the structure B. Soundness can be monitored.

(Collector)
As shown in FIG. 2, the collection device 5 includes a communication unit 51 that receives information from the sensor device 4 (information such as detection results of the magnetic sensor 2 and the vibration sensor 3), a storage unit 52, and a control unit. 53.

[Communication Department]
The communication unit 51 illustrated in FIG. 2 has a function of receiving measurement information transmitted wirelessly as described above. Although not shown, the communication unit 51 includes the same antenna and communication circuit as the communication unit 41 described above. The communication circuit of the communication unit 51 includes, for example, a reception circuit for receiving electromagnetic waves and a demodulation circuit having a function of demodulating a received signal. The communication circuit of the communication unit 51 includes a down-converter circuit having a function of converting a signal frequency to a low level, an up-converter circuit having a function of converting a signal frequency to a high level, and an amplifier circuit having a function of amplifying a signal. You may do it.

[Storage unit]
The storage unit 52 has a function of storing information such as measurement information, programs and data used for determination of soundness as described later (for example, vibration data related to the natural vibration of the structure B), and determination results regarding the obtained soundness. Have. The storage unit 52 is not particularly limited, and either a non-volatile memory or a volatile memory can be used.

[Control unit]
The control unit 53 has a function of controlling each unit constituting the collection device 5 and processing measurement information. The control unit 53 is configured by an MPU, for example.

  In particular, the control unit 53 has a function as a “determination unit” that determines the soundness of the structure B using the detection results of the magnetic sensor 2 and the vibration sensor 3. The determination of the soundness level will be described in detail together with a description of a structure monitoring method described later.

  The configuration of the collection device 5 has been described above. Although it does not specifically limit as a power supply which drives the collection apparatus 5 comprised in this way, For example, the secondary battery etc. which were connected to the commercial power supply and the solar cell can be used.

≪Structure monitoring method≫
Hereinafter, the structure monitoring method of the present invention will be described by taking the case of using the above-described system 1 as an example.

  FIG. 7 is a graph showing the relationship between the distortion of the metal part included in the structure and the strength of the magnetic field generated therewith. FIG. 8 is a graph showing the relationship between the magnetic field detected by the magnetic sensor and the amount of vibration detected by the vibration sensor.

  Since the metal part ST included in the structure B is generally composed of a general structural steel material typified by soft iron, it exhibits ferromagnetism. In such a metal part ST, as shown in FIG. 7, the magnetic field generated from the metal part ST changes with metal fatigue (strain). More specifically, the magnetic field generated from the metal part ST increases with the progress of metal fatigue (strain). For this reason, the fatigue level of the metal part ST can be determined using the detection result of the magnetic sensor 2.

  Further, when the metal fatigue of the metal part ST proceeds, the vibration amount (amplitude) of the structure B when the structure B is vibrated with a constant force increases. Therefore, when the magnetic field from the metal part ST based on the detection result of the magnetic sensor 2 increases as shown in FIG. 8 from the relationship between the metal fatigue and the vibration amount and the result shown in FIG. 7 described above, The amount of vibration of the structure B based on the detection result of the vibration sensor 3 increases. For this reason, when the amount of vibration detected by the vibration sensor 3 increases as the magnetic field detected by the magnetic sensor 2 increases, the vibration of the structure B is accompanied by metal fatigue of the metal part ST. It can be determined that the amount is increasing. Further, when the vibration amount detected by the vibration sensor 3 suddenly increases with respect to the change amount of the magnetic field detected by the magnetic sensor 2, the vibration of the structure B is caused by a factor different from the metal fatigue of the metal part ST. It can be determined that the amount is increasing. In addition, when the vibration amount detected by the vibration sensor 3 rapidly decreases after the predetermined amount or more, it can be determined that the structure B is broken (the vibration state of the structure B is abnormal). . Further, when the metal part ST breaks due to metal fatigue, the magnetic field generated from the metal part ST increases rapidly. Therefore, when it is determined that the structure B has been destroyed, when the magnetic field detected by the magnetic sensor 2 has increased abruptly, the cause of the destruction of the structure B is metal fatigue of the metal part ST (breakage of the metal part ST). It can be determined that Moreover, since the natural frequency of the structure B decreases as the deterioration of the structure B progresses, based on the vibration data of the structure B set in advance and the vibration frequency detected by the vibration sensor 3, The degree of progress of the deterioration of the structure B can also be determined.

  The soundness level of the structure B can be determined as described above. Hereinafter, a method of using the system 1 described above will be described.

  FIG. 9 is a flowchart for explaining a method of using the structure monitoring system shown in FIG. 1 (structure monitoring method).

  As shown in FIG. 9, the method for using the structure monitoring system (structure monitoring method) includes [1] a step of preparing the magnetic sensor 2 (step S1) and [2] attaching the magnetic sensor 2 to the structure B. Step (Step S2), [3] Step (Step S3) of detecting a magnetic field change due to metal fatigue of the metal part ST by the magnetic sensor 2, and [4] Structure using the detection result of the magnetic sensor 2. And a step of determining the soundness level of B (step S4).

  In step S1, the magnetic sensor 2 configured as described above is prepared. At this time, the sensor device 4 and the collecting device 5 configured as described above are prepared. Note that only the magnetic sensor 2 may be prepared, the sensor device 4 may be assembled, and the collection device 5 may be prepared after step S2 and before step S3.

  In step S2, the magnetic sensor 2 is attached to the structure B as described above. At this time, the vibration sensor 3 is also attached to the structure B as described above. Here, the attachment of these sensors may be performed by embedding the sensor before the concrete portion C is cured, or may be performed by perforating the concrete portion C after curing and embedding the sensor.

  In step S <b> 3, the sensor device 4 is operated to perform magnetic detection by the magnetic sensor 2. Thereby, the magnetic field from the metal part ST can be detected by the magnetic sensor 2. At this time, vibration detection by the vibration sensor 3 is also performed. Thereby, the vibration of the structure B can be detected. Here, at the time of vibration detection by the vibration sensor 3, vibration detection may be performed by exciting the structure B with a predetermined force from an external device or instrument, or natural vibration of the structure B (inherent Vibration) may be detected by the vibration sensor 3. The detection results of the magnetic sensor 2 and the vibration sensor 3 are transmitted from the sensor device 4 to the collection device 5 and collected by the collection device 5.

In step S4, the collection device 5 determines the soundness of the structure B using the detection results of the magnetic sensor 2 and the vibration sensor 3 as described above.
As described above, the soundness level of the structure B can be determined.

  According to the system 1 as described above, the magnetic field from the structure B including the metal part ST (more specifically, from the metal part ST to the metal fatigue using the energy transition characteristics of the alkali metal atoms. The fatigue state of the metal part ST of the structure B can be detected using the magnetic sensor 2 that detects the intensity of the generated magnetic field). Therefore, information on the fatigue state of the metal part ST can be included in the determination result of the soundness level of the structure B, and as a result, the soundness level of the structure B including the metal part ST can be monitored more accurately.

  Further, as described above, the control unit 53 of the collection device 5 determines the soundness level of the structure B using the detection result of the vibration sensor 3 in addition to the detection result of the magnetic sensor 2. Thereby, the information regarding the presence or absence of vibration abnormality of the whole structure B can be included in the determination result of the soundness level of the structure B.

  Moreover, the control part 53 compares the detection result of the vibration sensor 3, and the vibration data memorize | stored in the memory | storage part 52, and determines a soundness degree using the comparison result. Thereby, the presence or absence of vibration abnormality of the whole structure B can be determined easily and accurately and included in the determination result of the soundness level of the structure B.

Second Embodiment
Next, a second embodiment of the present invention will be described.

  FIG. 10 is a diagram showing a schematic configuration of a magnetic sensor used in the structure monitoring system according to the second embodiment of the present invention.

  Hereinafter, the second embodiment will be described with a focus on differences from the above-described embodiment, and description of similar matters will be omitted.

  The second embodiment is the same as the first embodiment except that the configuration of the magnetic sensor is different. In addition, the same code | symbol is attached | subjected to the structure similar to embodiment mentioned above.

  The magnetic sensor 2A used in this embodiment includes a light source unit 222A, a polarizing plate 261, a half mirror 262, an atomic cell 221, a mirror 263, a polarization separator 264, a light detection unit 225a, and a light detection unit 225b. And having. In FIG. 10, for convenience of explanation, the x axis, the y axis, and the z axis are indicated by arrows as three axes orthogonal to each other, and “+” indicates the tip side of the arrow and “−” indicates the base end side. The direction parallel to the x-axis is referred to as “x-axis direction”, the direction parallel to the y-axis is referred to as “y-axis direction”, and the direction parallel to the z-axis is referred to as “z-axis direction”.

  The light source unit 222 </ b> A emits light having a wavelength corresponding to the alkali metal absorption line in the atomic cell 221. The light source unit 222A is not particularly limited as long as it can emit light as described above. For example, a semiconductor laser such as a vertical cavity surface emitting laser (VCSEL) can be used.

  The polarizing plate 261 is an element that polarizes light from the light source unit 222A in a specific direction to make linearly polarized light.

  The half mirror 262 is an element that transmits light traveling in the −z-axis direction from the light source unit 222 </ b> A and reflects light traveling in the + z-axis direction from the atomic cell 221 in the direction toward the polarization separator 264. The half mirror 262 is, for example, a partially polarized beam splitter or a non-polarized beam splitter whose transmittance is constant regardless of the polarization direction.

  The mirror 263 is an element that reflects the light from the light source unit 222 </ b> A that has passed through the atomic cell 221 and enters the atomic cell 221 again. The mirror 263 has a reflective surface using a metal film or a dielectric multilayer film.

  The polarization separator 264 is an element that separates incident light into light of two polarization components orthogonal to each other. The polarization separator 264 is, for example, a Wollaston prism or a polarization beam splitter.

  Each of the light detection unit 225a and the light detection unit 225b is a detector having sensitivity to the wavelength of light from the light source unit 222A.

  In the magnetic sensor 2 </ b> A having such a configuration, the light emitted from the light source unit 222 </ b> A becomes linearly polarized light having a higher degree of polarization by the polarizing plate 261. The polarized light passes through the half mirror 262 and enters the atomic cell 221. Then, the light incident on the atomic cell 221 excites the alkali metal atoms enclosed in the atomic cell 221 (optical pumping). At this time, the polarization plane of light is rotated by receiving the polarization plane rotation action corresponding to the strength of the magnetic field. The light transmitted through the atomic cell 221 is reflected by the mirror 263 and enters the atomic cell 221 again. The light incident on the atomic cell 221 is again subjected to the polarization plane rotation action. The light transmitted through the atomic cell 221 is reflected by the half mirror 262 and separated into two polarized light components by the polarization separator 264. The light intensities of the two polarization components are detected by the light detection unit 225a and the light detection unit 225b, respectively.

  Here, the interaction between atoms and light (polarization plane rotation action) for magnetic field measurement is basically divided into three stages: a pump process, a precession process, and a probe process. Hereinafter, the function of the element at each stage will be described.

  For example, cesium is enclosed in the atomic cell 221, and the light from the light source unit 222A has a wavelength that excites the ultrafine structure quantum number of cesium from the ground state of F = 3 to the excited state of F ′ = 4, In the case of linearly polarized light having an electric field oscillating in the y-axis direction (electric field vector Ei), the outermost electrons of cesium are excited (optically pumped), and the angular momentum of the cesium atom (more precisely, the spin angular momentum) It is unevenly distributed along the electric field of incident light. At this time, since the electric field of the incident light vibrates along the y-axis direction, the angular momentum is distributed mainly in the + y-axis direction and the -y-axis direction. That is, the optically pumped cesium atom has two anti-parallel angular momentums of + y axis direction and -y axis direction. Here, the anisotropy generated in the distribution of angular momentum is widely referred to as “alignment”, and the generation of the anisotropic distribution in angular momentum is referred to as “forming alignment”. In other words, forming alignment is the same as magnetizing.

  When a static magnetic field is applied in the z-axis direction with the alignment formed as described above by optical pumping, the cesium atoms are parallel to the z-axis by the action of the static magnetic field and the alignment (parallel to the static magnetic field). A clockwise rotation force about the axis of rotation). This rotational force causes the cesium atom to rotate in the xy plane. This is precession. When the cesium atom rotates, the alignment rotates. Here, the rotation angle of the alignment based on the alignment in a state where no magnetic field is applied is α. For a single atom, the angular momentum bias (excited state) caused by pumping decreases with time, that is, the alignment is relaxed. Since the laser beam is CW light, alignment formation and relaxation are repeated in parallel and continuously. As a result, a steady (time-average) alignment is formed as a whole group of atoms. The rotation angle α of the alignment and the magnitude of the angular momentum depend on the precession frequency (Larmor frequency) and the relaxation rate determined by a plurality of factors.

  Due to such steady alignment, the light from the light source unit 222 </ b> A is subjected to linear dichroism in the atomic cell 221. The direction of alignment is the transmission axis, and the polarization component in this direction is mainly transmitted. The direction perpendicular to the alignment direction is the absorption axis, and the polarization component in this direction is mainly absorbed. That is, if the amplitude transmission coefficients of light on the transmission axis and the absorption axis are expressed as t‖ and t⊥, t‖> t⊥. The transmission axis component and the absorption axis component of the electric field Ei of incident light are Eicos α and Eisin α. The transmission axis component and absorption axis component of the electric field Eo after passing through the atomic cell 221 (after interacting with the cesium atom) are t‖Eicosα and t⊥Eisinα. Since t‖> t⊥, the electric field vector Eo rotates with reference to the electric field vector Ei (that is, the polarization plane of the laser beam rotates). This rotation angle is assumed to be φ.

  More precisely, a phenomenon occurs in which the angular momentum is biased in the propagation direction of the laser beam (Alignment Orientation Conversion, AOC), and as a result, rotation of the polarization plane (Faraday effect) due to circular birefringence occurs. Although this happens, this phenomenon is ignored here.

  As described above, the light whose polarization plane is rotated by the steady alignment is separated into two polarization components by the polarization separator 264. For example, these two polarization components are separated into components along two axes, a first detection axis and a second detection axis. The first detection axis is inclined + 45 ° with respect to the polarization plane when the polarization plane is not rotated (φ = 0). The second detection axis is inclined by −45 ° with respect to the polarization plane when the polarization plane does not rotate. The light detection unit 225a and the light detection unit 225b detect the light amounts of the components along the first detection axis and the second detection axis, respectively. The first detection axis component of the electric field vector Eo of the light transmitted through the atomic cell 221 is Eocos (π / 4-φ), and the second detection axis component is Eosin (π / 4-φ). Here, when the rotation of the polarization plane is almost zero (φ≈0), the intensity (light quantity) of light incident on the light detection unit 225a and the light detection unit 225b is substantially the same. Conversely, if there is a difference in the amount of light incident on the light detection unit 225a and the light detection unit 225b, it indicates that the plane of polarization is rotating. This means that there is a magnetic field. The difference in the amount of light incident on the light detection unit 225a and the light detection unit 225b is a function of the rotation angle φ of the polarization plane. By calculating the difference between the output signals of the light detection unit 225a and the light detection unit 225b, information on the rotation angle φ can be obtained. The rotation angle φ is a function of the applied static magnetic field. Therefore, information on the applied static magnetic field can be obtained from the rotation angle φ.

  The magnetic sensor 2A described above detects the strength of the magnetic field using the nonlinear magneto-optical effect of alkali metal atoms. Thereby, the magnetic field from the metal part ST can be detected with high accuracy using the magnetic sensor 2A.

  Although the structure monitoring system and the structure monitoring method of the present invention have been described based on the illustrated embodiment, the present invention is not limited to this.

  For example, in the present invention, the configuration of each part can be replaced with any configuration that exhibits the same function, and any configuration can be added.

  In the above-described embodiment, the case where the detection results from a plurality of sensors are collectively transmitted by one communication unit has been described as an example. However, a communication unit may be provided for each sensor. In this case, each communication unit may transmit information to the collection device 5, or at least one communication unit functions as a parent device and collects the transmission methods from the remaining communication units in a lump. You may comprise so that it may transmit to 5.

  In the above-described embodiment, the case where the detection result of each sensor is wirelessly transmitted to the collection device has been described as an example. However, the detection result of each sensor may be wired to the collection device.

DESCRIPTION OF SYMBOLS 1 ... Structure monitoring system 2, 2A, 2a, 2b, 2c ... Magnetic sensor 3, 3a, 3b, 3c ... Vibration sensor, 4 ... Sensor apparatus, 5 ... Collection apparatus, 20 ... Main-body part, 21 ... Package, 22 ... atomic cell unit, 23 ... support member, 41 ... communication unit, 42 ... storage unit, 43 ... control unit, 51 ... communication unit, 52 ... storage unit, 53 ... control unit, 211 ... base, 212 ... lid 214 ... Terminal, 221 ... Atom cell, 222 ... Light source unit, 222A ... Light source unit, 223 ... Optical component, 224 ... Optical component, 225 ... Photodetection unit, 225a ... Photodetection unit, 225b ... Photodetection unit, 226 ... Heater 227 ... Temperature sensor, 228 ... Substrate, 229 ... Holding member, 230 ... Adhesive, 231 ... Coil, 240 ... Amplifier, 241 ... Detector, 242 ... Modulator, 243 ... Oscillator, 244 ... Center Length control unit, 250 ... detection unit, 251 ... oscillator, 252 ... modulation unit, 253 ... oscillator, 254 ... frequency conversion unit, 255 ... detection unit, 256 ... oscillator, 257 ... modulation unit, 258 ... oscillator, 259 ... modulation unit , 261 ... Polarizing plate, 262 ... Half mirror, 263 ... Mirror, 264 ... Polarization separator, 290 ... Modulator, 2211 ... Body part, 2212 ... Light transmission part, 2213 ... Light transmission part, B ... Structure, C ... Concrete part, F, F1, F2, F3 ... floor, S ... internal space, S1 ... internal space, ST ... metal part, W, W1, W2, W3 ... wall

Claims (12)

A magnetic sensor that detects the strength of a magnetic field from a structure including a metal part using the energy transition characteristics of alkali metal atoms;
A structure monitoring system comprising: a determination unit configured to determine a soundness level of the structure using a detection result of the magnetic sensor. Comprising a vibration sensor for detecting the vibration of the structure,
The structure monitoring system according to claim 1, wherein the determination unit determines the soundness level using a detection result of the vibration sensor in addition to a detection result of the magnetic sensor. A storage unit for storing vibration data relating to the natural vibration of the structure;
The structure monitoring system according to claim 2, wherein the determination unit compares a detection result of the vibration sensor with the vibration data, and determines the soundness level using the comparison result.   The structure monitoring system according to any one of claims 1 to 3, wherein the determination unit determines a fatigue level of the metal portion using a detection result of the magnetic sensor. The magnetic sensor is
An atomic cell encapsulating an alkali metal;
A light source unit for irradiating light to the atomic cell;
A light detection unit for detecting the light transmitted through the atomic cell,
5. The structure monitoring system according to claim 1, wherein a main body unit including the atomic cell, the light source unit, and the light receiving unit is attached to the structure. 6. The magnetic sensor has a circuit unit electrically connected to the light source unit and the light detection unit,
The structure monitoring system according to claim 5, wherein the circuit unit is separated from the main body unit.   The structure monitoring system according to claim 5 or 6, wherein the atomic cell is included in the metal part when viewed from a direction in which the atomic cell and the metal part are arranged.   The structure monitoring system according to claim 1, further comprising a communication unit that wirelessly transmits a detection result of the magnetic sensor.   The structure monitoring system according to claim 8, wherein the communication unit is driven by electric power from a battery.   The structure monitoring system according to claim 1, wherein the magnetic sensor detects a magnetic field intensity using a nonlinear magneto-optical effect of the alkali metal atom.   The structure monitoring system according to claim 1, wherein the magnetic sensor detects the intensity of a magnetic field using an electromagnetically induced transmission phenomenon of the alkali metal atom. Preparing a magnetic sensor for detecting the strength of the magnetic field using the energy transition characteristics of alkali metal atoms;
Attaching the magnetic sensor to a structure including a metal part;
Detecting a change in the magnetic field due to fatigue of the metal part using the magnetic sensor;
And a step of determining a soundness level of the structure using a detection result of the magnetic sensor.

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